We are continuing to probe the molecular basis of immune recognition through the application of modern techniques of experimental cellular immunology to the genetically, defined murine model. The extremely well-characterized protein antigen, hen egg-white lysozyme (HEL), other avian and mammalian enzymes, peptide fragments of HEL, specifically derivatized HEL and synthetic peptides related to HEL, are all utilized in this study. In particular, we will examine: (1) The importance of limitations in the antigen presenting machinery vs. genetic or ontogenic gaps in the T repertoire as an explanation for the highly restricted nature of functional T cells. We will try to prepare peptide probes containing an anchorage site for the MHC restricting element as well as an epitypic site for T cell receptor binding. (2) We shall extend our studies of the fine specificity, idiotypy and amino acid sequences of a series of related anti-HEL hybridoma antibodies, relating idotypic to antigen-binding structures. (3) We shall also develop cloned T cell helper and suppressor lines, specific for HEL and continue to study a transformed suppressor line. These will be particularly useful in probing the molecular restrictions in both cooperative and suppressive cell-cell interactions. (4) The expressed repertoire of B cells will be studied as a function of collaboration with cloned T-helper cells of known specificities. These studies may eventually provided a basis for rational manipulation of the immune system.